Conditional formatting will achieve this. e.g. if you consider this example

reorder min end
200 50 49

click on the cell containing the reorder value, then click Format,
Conditional Formatting and change the Condition to "Formula Is" then enter
the formula
=C2<B2 then click the Format button and choose the color you want the
reorder cell to be.

"Alan" wrote:

I am trying to set up an automatic re-order system where the re-order column
shows the re-order amount in Red only when the End Balance column is less
than the Minimum Stock column. How do I do that?